1. Field of the Invention
The present invention relates to a process for the hermetic packages of various products, in particular food products, inside an envelope of flexible material, openable and re-closeable after each partial drawing of the product.
An apparatus for carrying out such process is a further object of the invention.
2. The Prior Art
As known, there are various types of air-tight packages currently available, in particular for easily perishable food products, consisting of envelopes generally of flexible material able to exclude the exposure of the product to the open air and at the same time to allow that the packaged product be recognised through inscriptions, designs and figures reported on the envelope. It is also known that the current air-tight envelopes for food products made of plastic material, cardboard and the like, while, on one side, have the advantage of resulting long lasting and of securing the air-tightness, on the other side, they turn out to be difficult to open, requiring for this operation the employment of scissors and knives, which can come out to be dangerous.
Moreover, the current hermetically sealed envelopes have the drawback that they cannot be re-sealed once they are opened to allow the partial drawing of the product. In the practice, this forces the user to seek expedients to try to close the product as hermetically as possible after each drawing, such as, for example, folding the open side of the package over itself, or wrapping the package inside plastics films or other sort of envelopes.
The possibility of using laminated plastics films or sheets for carrying out the air-tight wrapping of products of various types is also known; in such cases, an edge region of laminated film, closing the opening made in the envelope of the packaging carried out by means of the film itself, can be separated by detaching the same edge of the envelope as it were a peel; this hermetic packaging system is known in the packaging industry as "inside to outside sealing".
It is known in fact that the laminated plastics film is able to seal two overlapping layers of the same film by mutual adhesion, which layers can be separated from each other to open a package and re-seal it again, after each partial drawing of the product therein contained.
The only serious drawback present in the envelopes carried out by laminated and separable films is that they allow the formation of envelopes in an shape and size unique to each single type of products, in that the apparatuses currently employed for producing such a kind of packaging do not permit to produce different types of packages; said apparatuses have to undergo in fact conversions and structural modifications as well as regulations for producing the envelopes in different shapes and sizes, in order to adapt them to the various products.
DE-A-2939791, Beck, discloses a process for the production of a small bag which can be opened and closed again containing the product to be packed, characterised in that a thread of adhesive is stuck onto a first sheet, that a second sheet is applied on the first sheet, that the ensemble constituted by the first and the second sheet joined together is joined to a third sheet on which the product to be packed is placed; the ensemble is joined to the third sheet by means of two joints, an upper joint at the top of the bag and a lower joint at the bottom of the bag; finally the bag is sealed on the sides by means of a seam.
The apparatus for carrying out the process is constituted by a first spool from which the first sheet unfolds, by a second spool for the second sheet and by a third spool rotating in opposite direction, for the third sheet.
The bag obtained is provided with an upper sealing line joining the second sheet to the third sheet, a lower sealing line joining the first sheet to the third sheet and an adhesive line joining the second sheet to the first sheet.
U.S. Pat. No. 3,022,613, Powers discloses a process for packaging a product comprising forming a continuous envelope from a continuous wide web of heat-sealable sheet, formed by longitudinally folding the web on a longitudinal fold line to provide a first and a second superimposed walls, integrally joined, and providing a marginal portion which is folded on a longitudinal fold line constituting a flap-forming portion.
According to a variation of the process the envelope is formed from two individual webs of the same material, heat sealing the webs along an edge of the envelope, so forming a lower joint at the bottom of the envelope. According to another variation, the envelope is formed from two individual webs and a tape, each of heat sealable sheet, heat sealing the webs and the tape, so forming a lower joint at the bottom of the envelope and an upper joint at the top of the envelope.